I am having a lot of trouble understanding acid-base reactions. I was able to struggle through most of the homework, but I'm not usre about these questions.

Question

1) Can an acidic solution be made less acidic by adding an acidic solution?

2) Pennies manufactured after 1982 are made of zinc metal, Zn, within a coat of copper metal, Cu. Zinc is more easily oxidzed than copper. Why, then, don't these pennies quickly corrode?

Is this because the copper has more of an affinity for the underlying zinc than the oxygen around it?

3) Chemical equations need to be balanced not only in terms of the number of atoms, but also by the charge. In other words, just as the same number of atoms should appear before and after the arrow of an equation, so should the same charge. Take this into account to balance the following chemical equation:

Sn2+ + Ag ----> Sn + Ag+

The charge looks balanced to me. There is a positive charge on the left and the right. All I see is that an Sn atom is missing on the left. So maybe the equation should read:
Sn2+ + Ag --- Sn + SnAg+ ?

Thanks for your help - this is my last homework assignment in this class, and I can tell I won't be pursuing chemistry or physics in my studies - lol!

Answer 1

1. If you add a more dilute acid, the ...

2. Copper and zinc form brass, which does not corrode. AT the juncture of the Zn-Cu interface, brass is formed.

3.Balancing by electrons and mass is a complication. In yours, you have two electrons missing on the left (the Sn⁺², on only one on the right...so where did the electron come from. I would balance it this way..

Sn⁺²+2Ag>>Sn + 2Ag⁺¹

all that means is each of the Ag atoms donated one electron to the Sn⁺² ion

It is now balanced in mass, and in charge.

Answer 2

If you want extra credit, figure out why brass is non-corrosive.

Answer 3

Perhaps brass is noncorrosive because the zinc and copper are locked into an alloy, or solid solution, that will not release any electrons to allow for oxidation?

Thanks for the help, too! :-) Mary